Arc Flash, Coordination and Short Circuit Study for a Truss and Wall Panel Plant With Four Utility Services, Pflugerville (2025)

A manufacturer of roof trusses and wall panels in Pflugerville runs four buildings on one site, and each has its own utility service. In March 2025 we finished an arc flash, coordination and short circuit study of the truss plant that put all four buildings into one model.

Four services, four layouts

The wall panel plant takes its service through a 225 kVA transformer. The truss plant service drops to a 400 A safety disconnect switch. The shipping and receiving building is fed underground, and the main office overhead. Inside, the plants run at 480 V, with 240 V and 208 V panels for lighting and smaller loads. The ETAP^® model held 231 buses: 92 at 480 V, 97 at 208 V, the rest at 240 V and other voltages, plus the three 12.47 kV utility points.

Gaps in the data

Not every breaker could be opened and read, and not every cable could be traced. Where breaker data was missing, the breaker was modeled with no trip function, which assumes the next device upstream clears the fault and so errs high. Where a cable could not be reached, we estimated the size it would need. We obtained the utility data ourselves and checked it against IEC 60076-5 where needed.

Results

The highest incident energy, about 58 cal/cm², was at the three 12.47 kV utility points, above the 40 cal/cm² level where arc rated clothing is no longer considered adequate. Inside the plants the highest were about 21 cal/cm², at two 480 V panels. In all, 21 buses were above 8 cal/cm², and 180 of the 231 fell in the lowest energy level. No critical items were found and no setting changes were proposed. Labels follow the energy levels of NFPA 70E^® Annex H.

Related services

For the modeling side, see our arc flash study services. Device settings are covered under protection coordination.